util/rational: some more refactoring

src/codec/decoder/mod.rs

@@ -105,14 +105,14 @@ impl Decoder {
 				None
 			}
 			else {
-				Some(Rational(value))
+				Some(Rational::from(value))
 			}
 		}
 	}
 
 	pub fn time_base(&self) -> Rational {
 		unsafe {
-			Rational((*self.as_ptr()).time_base)
+			Rational::from((*self.as_ptr()).time_base)
 		}
 	}
 }

src/codec/decoder/video.rs

@@ -56,7 +56,7 @@ impl Video {
 
 	pub fn aspect_ratio(&self) -> Rational {
 		unsafe {
-			Rational((*self.as_ptr()).sample_aspect_ratio)
+			Rational::from((*self.as_ptr()).sample_aspect_ratio)
 		}
 	}